1. Field of the Invention
The present invention relates to an image forming apparatus, and in particular relates to an image forming apparatus having a liquid ejection head that ejects liquid from a nozzle.
2. Description of the Related Art
In recent years, inkjet recording apparatuses (inkjet printers) have become widespread as image forming apparatuses for forming images such as pictures and documents on recording media. An inkjet recording apparatus forms a desired image on a recording medium by ejecting ink droplets onto the recording medium from nozzles in a head while causing the relative movement between the head and the recording medium.
In an inkjet recording apparatus, in particular in the case where a head for which singling (division printing) is not possible, such as a line head in which a large number of nozzles are arranged over a length in a width direction of the recording medium, is used, streakiness caused by the displacement of landing positions of dots deposited on the recording medium is a large issue. The cause of such displacement of the dot landing position includes, for example, the positions or shapes of nozzles deviating from an ideal state at the head manufacturing stage, and the poor liquid repellency in the vicinity of nozzles.
For example, Japanese Patent Application Publication No. 2004-58283 discloses technique to reduce such streakiness caused by landing position errors. According to an apparatus disclosed in Japanese Patent Application Publication No. 2004-58283, defective nozzles for which the landing position is displaced are determined, and the deposition amount (number of dots or ejection amount) for the defective nozzles and nozzles adjacent thereto is changed so as to suppress the visibility of streakiness.
However, according to the method described in Japanese Patent Application Publication No. 2004-58283, the streakiness is merely made less conspicuous on the basis of the characteristics of human vision, and it is difficult to carry out suitable correction over a broad density range from low density areas to high density areas.